There's a hole the size of a pencil in that hard plastic piece causing a vacuum leak.
What the hell is that so I can replaced it?
Nobody around here seems to know.

 

It's a 2003 Honda Civic Si ep3 if that helps.

 

I guess that would be your PCV valve.

 

naw, pcv is next to the alternator on the other side of the engine.

haven't been able to locate that part yet though, I've found the housing it goes into, but not that part.

 

Air control valve.

 

Fast idle thermal air control switch. Allows additional air to be injected into the intake manifold until the engine warms up to above 140 degrees F. Once this threshold is reached, the valve closes the air path and the idle drops down to normal.

The unit you have pictured is broken... there is normally a fitting facing the drivers fender that connects a hose to the intake pipe where it draws fresh filtered air before the T/B.

 

Thank you JR!
I actually just got an RSX yesterday and saw the intact part so I know the nipple on the side going to the intake but still had no clue what it was called.